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How did placentals out compete marsupials and monotremes outside of australia
Topic Started: Dec 7 2017, 02:39 PM (1,060 Views)
tatsuslava
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So how did placental mammals out compete marsupials and monotremes outside of Australia exactly? What made them more efficient ?
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Claudiu Constantin Nicolaescu
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I think the placental mammals have bigger brains than the monotremes and the marsupials. This is a big advantage to adapt better to a changing environment.
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tatsuslava
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But how so exactly is there a reason behind That?
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Claudiu Constantin Nicolaescu
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Just like that. I give you an example: the dingo (Canis dingo) is smarter and more adaptable than the thylacine (Thylacinus cynocephalus). As a result, the dingo replaced the thylacine in Australian mainland.
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Ausar
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More recent evidence suggests thylacines on the mainland of Australia were not driven to extinction by dingos.

http://onlinelibrary.wiley.com/wol1/doi/10.1111/jbi.13101/abstract
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Meancat
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Claudiu Constantin Nicolaescu
Dec 7 2017, 04:25 PM
I think the placental mammals have bigger brains than the monotremes and the marsupials. This is a big advantage to adapt better to a changing environment.
True, placental brains are 2.5 times bigger than marsupial brains. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564077/
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tatsuslava
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Meancat
Dec 9 2017, 02:08 PM
Claudiu Constantin Nicolaescu
Dec 7 2017, 04:25 PM
I think the placental mammals have bigger brains than the monotremes and the marsupials. This is a big advantage to adapt better to a changing environment.
True, placental brains are 2.5 times bigger than marsupial brains. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564077/
Yes but why? How exactly does that happen?
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Ryo
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tatsuslava
Dec 9 2017, 02:11 PM
Meancat
Dec 9 2017, 02:08 PM
Claudiu Constantin Nicolaescu
Dec 7 2017, 04:25 PM
I think the placental mammals have bigger brains than the monotremes and the marsupials. This is a big advantage to adapt better to a changing environment.
True, placental brains are 2.5 times bigger than marsupial brains. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564077/
Yes but why? How exactly does that happen?
I recall it having something to do with the way they give birth. When the baby stays inside the mother as Placentals do, they got more energy from the mother to develop larger brains, while Marsupials crawl out and into the pouch as nearly fosters. Marsupials have their own sets if advantages however, with not ever being actually pregnant and thus vulnerable to predators.

Tasmanian Devils are among the only Marsupials who seems to have an evolutinary advanage over similar sized placentals.
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Taipan
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Meancat
Dec 9 2017, 02:08 PM
Claudiu Constantin Nicolaescu
Dec 7 2017, 04:25 PM
I think the placental mammals have bigger brains than the monotremes and the marsupials. This is a big advantage to adapt better to a changing environment.
True, placental brains are 2.5 times bigger than marsupial brains. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564077/


Ryo
Dec 9 2017, 02:34 PM
tatsuslava
Dec 9 2017, 02:11 PM
Meancat
Dec 9 2017, 02:08 PM
Yes but why? How exactly does that happen?
I recall it having something to do with the way they give birth. When the baby stays inside the mother as Placentals do, they got more energy from the mother to develop larger brains, while Marsupials crawl out and into the pouch as nearly fosters. Marsupials have their own sets if advantages however, with not ever being actually pregnant and thus vulnerable to predators.

Tasmanian Devils are among the only Marsupials who seems to have an evolutinary advanage over similar sized placentals.


Its not brain size:

"The evolution of mammalian brain size is directly linked with the evolution of the brain's unique structure and performance. Both maternal life history investment traits and basal metabolic rate (BMR) correlate with relative brain size, but current hypotheses regarding the details of these relationships are based largely on placental mammals. Using encephalization quotients, partial correlation analyses, and bivariate regressions relating brain size to maternal investment times and BMR, we provide a direct quantitative comparison of brain size evolution in marsupials and placentals, whose reproduction and metabolism differ extensively. Our results show that the misconception that marsupials are systematically smaller-brained than placentals is driven by the inclusion of one large-brained placental clade, Primates.

"Regressions of marsupial and placental brain size against body size confirmed that the brain size of marsupials is not systematically smaller than that of similar-sized placentals (49, 50, 53). Moreover, small marsupials not only overlap with placentals in relative brain size (see also ref. 49), but also are larger-brained on average than similar-sized placental species (which might explain the outstanding performance of tiny dasyurids in cognition tests; ref. 54).


Brain size, life history, and metabolism at the marsupial/placental dichotomy


Ryo
Dec 9 2017, 02:34 PM

Tasmanian Devils are among the only Marsupials who seems to have an evolutinary advanage over similar sized placentals.


That evolutionary advantage is?
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Claudiu Constantin Nicolaescu
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But if marsupial and monotreme mammals are as smart or even smarter than placental mammals, why we do not have today or in the fossil record any domesticated marsupials and monotremes? And why marsupials and monotremes did not evolved into human-like intelligent species and societies in their splendid isolation on the Southern Hemisphere, or in the Northern Hemisphere where they coexist with placental mammals, including humans?
Edited by Claudiu Constantin Nicolaescu, Dec 9 2017, 10:48 PM.
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Ryo
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Taipan
Dec 9 2017, 09:09 PM
Meancat
Dec 9 2017, 02:08 PM
Claudiu Constantin Nicolaescu
Dec 7 2017, 04:25 PM
I think the placental mammals have bigger brains than the monotremes and the marsupials. This is a big advantage to adapt better to a changing environment.
True, placental brains are 2.5 times bigger than marsupial brains. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1564077/


Ryo
Dec 9 2017, 02:34 PM
tatsuslava
Dec 9 2017, 02:11 PM
I recall it having something to do with the way they give birth. When the baby stays inside the mother as Placentals do, they got more energy from the mother to develop larger brains, while Marsupials crawl out and into the pouch as nearly fosters. Marsupials have their own sets if advantages however, with not ever being actually pregnant and thus vulnerable to predators.

Tasmanian Devils are among the only Marsupials who seems to have an evolutinary advanage over similar sized placentals.


Its not brain size:

"The evolution of mammalian brain size is directly linked with the evolution of the brain's unique structure and performance. Both maternal life history investment traits and basal metabolic rate (BMR) correlate with relative brain size, but current hypotheses regarding the details of these relationships are based largely on placental mammals. Using encephalization quotients, partial correlation analyses, and bivariate regressions relating brain size to maternal investment times and BMR, we provide a direct quantitative comparison of brain size evolution in marsupials and placentals, whose reproduction and metabolism differ extensively. Our results show that the misconception that marsupials are systematically smaller-brained than placentals is driven by the inclusion of one large-brained placental clade, Primates.

"Regressions of marsupial and placental brain size against body size confirmed that the brain size of marsupials is not systematically smaller than that of similar-sized placentals (49, 50, 53). Moreover, small marsupials not only overlap with placentals in relative brain size (see also ref. 49), but also are larger-brained on average than similar-sized placental species (which might explain the outstanding performance of tiny dasyurids in cognition tests; ref. 54).


Brain size, life history, and metabolism at the marsupial/placental dichotomy


Ryo
Dec 9 2017, 02:34 PM

Tasmanian Devils are among the only Marsupials who seems to have an evolutinary advanage over similar sized placentals.


That evolutionary advantage is?
The thing that helped them wipe feral cats and Foxes out from Tasmania. Usually, they have to follow another Marsupial, hoping they will drop their young. One thing is that Placentals are often more vulnerable when pregnant, but that is an advantage for most Marsupials. Another thing is that Foxes have to leave their Cubs behind in a den while looking for food. Fox dens as I recall reading are quite smelly, and thus even further easier for a Tassie which have an excellent sense of smell to find. The Tassies find it easier to just raid a Fox den instead of following a Marsupial hoping that it drops its young. They did the same thing with Feral Cats I think.

Which because of this, is the only Marsupial I know of who is actually doing better than the invasive fauna in its size range that usually makes lots of other Marsupials extinct in quite the speed.
I can just imagine what would happen if Tassies were introduced to Australia if we minus the Feral Dogs.
Ryo
Dec 9 2017, 02:34 PM
tatsuslava
Dec 9 2017, 02:11 PM
Meancat
Dec 9 2017, 02:08 PM
Yes but why? How exactly does that happen?
I recall it having something to do with the way they give birth. When the baby stays inside the mother as Placentals do, they got more energy from the mother to develop larger brains, while Marsupials crawl out and into the pouch as nearly fosters. Marsupials have their own sets if advantages however, with not ever being actually pregnant and thus vulnerable to predators.

Tasmanian Devils are among the only Marsupials who seems to have an evolutinary advanage over similar sized placentals.
Replied to the wrong comment, meant this " But if marsupial and monotreme mammals are as smart or even smarter than placental mammals, why we do not have today or in the fossil record any domesticated marsupials and monotremes? And why marsupials and monotremes did not evolved into human-like intelligent species and societies in their splendid isolation on the Southern Hemisphere, or in the Northern Hemisphere where they coexist with placental mammals, including humans?"
Human like intelligence only went to one group of mammals which were primates (and to some extent maybe Dolphins and Elephants), however, there are 2 Marsupials living with humans and Placentails. 1 being the American Opossum, and the other which you could say is on trial is the Red-Necked Wallaby of England (and a few other places of Europe I think). Red Kangaroos seems to do just fine in Australia tho.
Edited by Ryo, Dec 9 2017, 11:26 PM.
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Claudiu Constantin Nicolaescu
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The Tasmanian devil (Sarcophilus harrisii) used to live also in mainland Australia, but went extinct here, surviving only in Tasmania. Maybe the arrival of humans and their commensal species contributed to this extinction event. I wonder why feral cats (Felis catus) living in Tasmania do not find a safe place in trees to raise their young.


Also, I wonder why, if the reproductive style of monotremes and marsupials is more competitive than the placental style, the placental mammals (including humans) are still hanging around? In this kind of logic, the monotremes and marsupials should be the invasive species worldwide, and the placentals should be the endangered living fossils.
Edited by Claudiu Constantin Nicolaescu, Dec 10 2017, 12:21 AM.
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Ausar
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Claudiu Constantin Nicolaescu
Dec 9 2017, 10:42 PM
But if marsupial and monotreme mammals are as smart or even smarter than placental mammals, why we do not have today or in the fossil record any domesticated marsupials and monotremes? And why marsupials and monotremes did not evolved into human-like intelligent species and societies in their splendid isolation on the Southern Hemisphere, or in the Northern Hemisphere where they coexist with placental mammals, including humans?
The overwhelming majority of placentals, among them some of the smartest, have never been truly domesticated. An even greater number of them failed to evolve human-like intelligence. That’s because the evolutionary parameters certain species have evolved under have either allowed or disallowed either of these two things, not because of some inherent placental advantage in intelligence.
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Claudiu Constantin Nicolaescu
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Ok, I give up! I hope that some day the placental mammals worldwide will be replaced by their monotreme and marsupial counterparts, which are today on the verge of extinction for unknown reasons. Evolution can be very tricky and surprising.
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Meancat
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Carnivorans, not just primates, have larger brains than marsupials. "Differences between these two groups may relate to brain volumes, which, in carnivorans, are around two and a half times that of marsupial carnivores"
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